import java.util.Scanner;

public class Six {

	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (scan.hasNextDouble()){
			double a,mid=0,begin=0;
			a=scan.nextDouble();
			double end=a;
			if(a>0&&a<1)
				end=1;
			if (a < 0) {
				System.out.println("error!please enter again:");
			}
			else{
				
				while(begin<=end){
					mid=(begin+end)/2.0;
					if(Math.abs((a-Math.pow(mid, 2)))<0.0000001)
						break;
					else if(Math.pow(mid, 2)<a)
						begin=mid+0.0000001;
					else if(Math.pow(mid, 2)>a)
						end=mid-0.0000001;
			    }
				System.out.printf("%.6f\n",mid);
			}
		}
		scan.close();
	}
}
